Woodland Watch – Week 7 – 01/05/2013

It has been such a late year for all of the plants coming out of their dormant winter stage, but the growth is definitely well under way now. One of the new plants observed emerging from the woodland floor this week is the male fern (Dryopteris fillis-mas). Native to much of europe, asia and North America, it favours damn, shaded areas in the understorey of woodlands.

Emerging male fern

Emerging male fern

The leaves of the male fern grow to a maximum length of 150cm and are bipinnate made up of around 20-35 pinnae (individual leaves) on each side of the central rachis (main axis). The stalks of the fern are covered in orange-brown scales.Between August and November the membranous outgrowth on the under surface of the fern leaves, which protects the developing spores, starts to shrivel and the spores are released.

Of the large trees in the woodland, the horse chestnut (Aesculus hippocastanum) is also starting to come into leaf.

Young horse chestnut leaves

Young horse chestnut leaves

The horse chestnut has large, red-brown sticky buds which start to emerge around April time, however this year they are late emerging due to the cold weather. The sticky sap on horse chestnut buds protects them from frost damage and insects.

Horse chestnuts are currently suffering from the leaf miner moth (Cameraria ohridella) which was originally found on horse chestnut trees in London. The larvae burrows within the leaf tissue, heavily infesting the leaves resulting in browning and drying and over time, leaf death. First observed in macedonia in 1985, the horse chestnut leaf miner moth has spread through central and eastern europe, first making an appearance in Great Britain in 2002.

We will keep an eye on the horse chestnut trees in the woodland over the coming months.

As the season progresses and the weather starts to warm up the nettles on the woodland floor are really starting to take hold.

Young nettles emerging all over the woodland floor

Young nettles emerging all over the woodland floor

Stinging nettles (Urtica dioica) can grow to 1-2m tall in the summer, dying back to the ground in winter. They spread rhizomes and stolons which are bright red like the plants roots and help the plant to take hold over large areas. The underside of the leaves and the stem are covered in stinging hairs whose tips come off when touched and act as a needle, injecting chemicals into the skin. These chemicals include acetylcholine, histamine, 5-HT (serotonin), moroidin, leukotrienes and possibly formic acid. The chemical mixture causes a painful stong from which the species derives its common name.

Join us next week for another installment of Woodland Watch.

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